Pressure regulators are employed in many different applications when a source of compressed gas is connected to a device which uses the compressed gas for different purposes
A common principle in a pressure regulator is that the inlet pressure is reduced on a regulator seat by an actuator or regulator piston. The regulator piston sets a clearance at the seat to achieve an outlet pressure defined by a force from a regulating elastic element. The regulator piston is loaded by the following forces: the force from the area pressurized by the inlet pressure, the force from the regulating elastic element, the force from the area pressurized by the outlet pressure, the reaction force from the regulator seat—in case the piston is in contact with the seat—and friction forces affecting the piston. In each regulator state all these forces are in balance, meaning that when the force resulting from the area pressurized by inlet pressure changes—e.g. as gas in the cylinder is consumed and the inlet pressure changes—the force resulting from the area pressurized by the outlet pressure changes as well. This is even more noticeable in pressure regulators for high flow capacity since they require a large boring of the seat which further increases the force resulting from the area pressurized by the inlet pressure. This described characteristic is usually referred to as the irregularity or stability of a pressure regulator. For the pressure outlet usability it is important to minimize the influence of the inlet pressure changes as much as possible since outlet pressure changes can negatively affect the performance of the devices connected to the pressure outlet.